DESCRIPTION: (Applicant's Abstract) The long term objectives of this proposal are to develop high resolution autoradiographic procedures, especially for use with the scanning electron microscope (ScEM). These are then to be applied together with other cellular and molecular techniques, to the study of specific problems in neurocytology. The proposed technical advances involve: the use of reversible (soluble) probes for labeling molecules for which no irreversible probes are yet available, calibrating the sensitivity and resolution of the technique, and devising methods for analyzing autoradiograms from thick specimen after in situ hybridization. The surface molecules to be studied are the voltage sensitive sodium channels on muscle and nerve cells, and the nicotinic acetylcholine receptors (AChRs) both on myotubes in culture, and on neurons; ScEM autoradiography will also be applied to analyze the perinuclear distributions of AChR and ACh esterase (AChE) transcripts in muscle during development and at the adult neuromuscular junction. Since the interactions between cells of the nervous system underlie a wide variety of mental, emotional and behavioral processes, information on the quantitative distribution of the molecules involved in those interactions should provide a wider understanding of the mechanisms involved.